British cities 'could be up to 10C hotter than countryside by 2100'

British cities could experience summer temperatures up to 18F (10C) higher than the surrounding countryside by 2100 due to global warming, according to Met Office research.

By Stephen Adams

3:21PM BST 10 May 2009

Periods of dangerously hot weather such as that which occurred in August 2003 could also become regarded as "the average" by 2040 and "relatively cool" by 2100.

Between August 4 and 13 2003 the day time temperature exceeded 86F (30C) every day.

But it was the high night time temperatures – up to 16.2F (9C) warmer in London than rural areas, and up to 12.6F (7C) higher in Birmingham and Manchester – that are believed to have killed many old people.

Now the Met Office is predicting that such differences in temperatures, known as the 'urban heat island' effect, could be exacerbated by global warming.

The principal cause of urban heat islands is that hard surfaces like buildings and roads reflect more light than vegetation, which is converted into heat.

The city high energy uses – such as car engines and air conditioning systems – push up temperatures further still.

Vicky Pope, head of climate change advice, said as global temperatures rose cities would consume more energy trying to keep cool, which would ironically push their temperatures up a degree or two.

She said: "As the climate gets warmer, sweltering summer temperatures will combine with rising energy use, the heat-retaining properties of buildings, and the sheer volume of people, to push temperatures higher and higher. It may sometimes make life in the metropolis intolerable."

She added: "We are looking at 2003 conditions becoming more like the average in 2040 and perhaps unusually cool in 2100."

This could cause major problems for health services. Between 4 and 13 August 2003, 2,091 more people than normal died, many because their bodies could not cope with continuously high temperatures. Periods of dangerously hot weather such as that which occurred in August 2003 could also become regarded as "the average" by 2040 and "relatively cool" by 2100.

Between August 4 and 13 2003 the day time temperature exceeded 86F (30C) every day.

But it was the high night time temperatures – up to 16.2F (9C) warmer in London than rural areas, and up to 12.6F (7C) higher in Birmingham and Manchester – that are believed to have killed many old people.

Now the Met Office is predicting that such differences in temperatures, known as the 'urban heat island' effect, could be exacerbated by global warming.

The principal cause of urban heat islands is that hard surfaces like buildings and roads reflect more light than vegetation, which is converted into heat.

The city high energy uses – such as car engines and air conditioning systems – push up temperatures further still.

Vicky Pope, head of climate change advice, said as global temperatures rose cities would consume more energy trying to keep cool, which would ironically push their temperatures up a degree or two.

She said: "As the climate gets warmer, sweltering summer temperatures will combine with rising energy use, the heat-retaining properties of buildings, and the sheer volume of people, to push temperatures higher and higher. It may sometimes make life in the metropolis intolerable."

She added: "We are looking at 2003 conditions becoming more like the average in 2040 and perhaps unusually cool in 2100."

This could cause major problems for health services. Between 4 and 13 August 2003, 2,091 more people than normal died, many because their bodies could not cope with continuously high temperatures.